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NC-v4 EAp2:Minimum energy performance

Outdoor Air when Baseline has System 2

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Green Lab
LEEDuser Basic Member
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I am following v4 and ASHRAE 90.1 - 2016.

I have an Hotel in Climate Zone 3A, therefore I am using System 2 (PTHP) for Baseline.

In the Hotel, there are VRFs and centralized Outdoor Air (OA) ventilation through FAHUs.

How can I consider the OA in the Baseline model? Should I design an centralized air loop to provide OA? or Should I consider PTHP with local OA supply? 

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Marcus Sheffer
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7group / Energy Opportunities
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Thu, 06/03/2021 - 15:03

You never design the baseline system. Model it as required in Appendix G. Unless any exceptions to G3.1.1 apply you model the whole building with PTHPs.
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Green Lab
LEEDuser Basic Member
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Fri, 06/04/2021 - 09:23

I am using Desgin Builder and although the default for the DB's system 2 HVAC design is a version without any fresh air intake, I'm wondering how fresh air can be brought into the building. My question is regarding appendix G, does it preview a fresh air intake from the local unit? Or the baseline in this case doesn't have fresh air intake at all?
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Marcus Sheffer
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Fri, 06/04/2021 - 15:51

Yes the OA comes in through the local unit. That is usually how a PTHP works.
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Tristan Roberts
Representative
Vermont House of Representatives
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Thu, 06/10/2021 - 11:40

Good to see you out here, Marcus! I'm replying to this thread just so our profile pics can visit... it's been a while! I hope all is well on the farm restoration project.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Thu, 06/10/2021 - 14:06

Hey Trinstan, good to hear from you. A lot has happened in my life in the past two yeras or so, basically it was turned upside down but in a very good way. No longer at the farm but am loving life even more. Hope all is well with you!
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Green Lab
LEEDuser Basic Member
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Tue, 06/15/2021 - 17:30

Glad I could help you reconnect with each other.
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Amgad Khattab
Managing Partner
Engineering Solutions
LEEDuser Basic Member
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Wed, 05/07/2025 - 13:26

Marcus Sheffer
Could you clarify your statement, "Yes, the OA comes in through the local unit. That is usually how a PTHP works"?
Are you referring to a dedicated fresh air fan for each unit, or does this imply a fresh air system serving the entire building?
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Marcus Sheffer
LEED Fellow
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LEEDuser Expert
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Thu, 05/08/2025 - 15:44

A packaged terminal heat pump is usually a direct, through the wall unit with a fresh air intake (a vent or damper) that brings in the outside air for each unit separately, not necessarily for the entire building.

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